The following question has been occupying (not only) the boating world since the beginning of the year: Which skippers can safely refuel with E10 biofuel and which cannot? But before we clarify this, let us briefly explain what E10 petrol is all about. The E stands for ethanol (alcohol obtained from plant matter) and the 10 indicates the maximum percentage blend.
This means that even more ethanol is added to the premium fuel (95 octane), which currently contains up to 5 per cent ethanol, to create the new E10. This fuel is intended to reduce the CO2 emissions of petrol engines. A good idea, if it weren't for the fact that the compatibility of the fuel for engines, including boat engines and other affected boat systems, is sometimes poorly or not at all clarified. What can the fuel do in unsuitable systems, for example in the tank?
Among other things, ethanol has the properties of solvents, which can attack the inside of older boats with plastic tanks. The same applies to the rest of the fuel system, such as rubber hoses, seals and filters. Aluminium, stainless steel and more modern plastic tanks have less of a problem with "dissolving".
There is a greater risk of clogged filters and pipes due to dirt dissolved in the tank. Another special feature of E10 is that it is hygroscopic, i.e. it attracts water and binds it. This is a property that can be particularly expensive for boat owners, as the fuel dilutes during long periods of inactivity, which can cause corrosion damage to the tank and pipes, but also inside the engine and in engine parts such as the carburettor, valve seats, cylinder liners or injection system. In the worst case, this can lead to engine failure or even engine damage.
To counteract this, frequent drivers who use E10 fuel will have to increase the maintenance intervals and therefore visit the workshop more often. In order to clarify which engines are actually suitable for E10, we asked the engine manufacturers. We also wanted to know what you need to bear in mind when running on E10.
Evinrude announces that running the engines on E10 would not cause any problems if the customer uses the fuel qualities specified by BRP/Evinrude for their engine. Yamaha has stated that all outboards built from 2003 onwards can be run on E10 without any restrictions. The installation of a fuel filter with water separator is recommended. All models prior to 2003 cannot be converted to run on E10 and are therefore reliant on other types of fuel.
According toHonda the use of a maximum of 10 per cent alcohol-containing fuel is generally possible. Therefore, the operation of Honda outboards with E10 petrol, which is 95 octane, is permitted. Honda also says that E10 reacts more strongly to factors such as exposure to light, ambient temperature and storage time. These could change the nature of the petrol and make it unusable more quickly. The company therefore recommends only using E10 fuel that is not older than 30 days and has been stored in an approved fuel container to ensure petrol quality.
Volvo Penta/Tohatsu explains that all engines can be fuelled with E10. Volvo also recommends installing a fuel filter with a water separator, which must then be checked for water and impurities according to the filter manufacturer's instructions and maintenance intervals. According to Volvo, a stabiliser such as Stabil should also be added when storing fuel with an ethanol content.
Mercury/MerCruiser provides the following information: The components of the fuel system of Mercury marine engines are designed to withstand fuels with an ethanol content of up to 10 % in petrol. Mercury also points out that phase separation is favoured due to the water-attracting property and the longer storage time.
The consequences can be increased corrosion of metal parts, wear of rubber and plastic parts, leaks in rubber fuel lines and starting and operating difficulties. For this reason, it is recommended to use fuels without ethanol content if this is possible. When using E10, the fuel system should be checked more frequently for leaks and anomalies.
Suzuki states that the use of E10 is possible for all four-stroke engines from the 1996 production date. With the exception of the DT8, DT8C, DT9.9C and DT15C models, there are also no restrictions on the use of E10 in Suzuki two-stroke engines. The text also states that the use of E10 on models with carburettors can lead to poorer engine running behaviour in individual outboards despite approval. In such cases, please do not continue to use E10.
As with Honda, E10 that has been stored in the fuel tank for longer than 30 days should no longer be used. If the outboard motor is not used for a longer period of time, the fuel should be drained from the vapour bubble separator or from the float chamber.
The question remains as to how tanks, hoses and tank sensors react to E10. To clarify this, we asked five large boatyards, dealers and workshops how their boat systems tolerate E10 fuel and whether it is necessary and possible to convert to the new fuel. We received consistently unsatisfactory answers: "Unfortunately, it seems that our suppliers, whether manufacturers or distributors, are keeping a low profile. Clear statements are not available. As a result, we are unable to provide a satisfactory answer to the numerous enquiries from our customers," said a well-known shipyard. Tank sensor manufacturer VDO is clearer: "Our level sensors are not approved for E10 fuels," they say.
We were also interested in the availability of E10 fuel at boat petrol stations. The water petrol stations we surveyed stated that they did not want to switch to the new biofuel, nor offer the fuel in addition to their existing range. The main reason for this attitude is the limited shelf life. E10 will therefore only be available for canister tankers at road petrol stations for the time being.
Conclusion:Operating boats with E10 is more complex than with other fuels if the skipper adheres to the engine manufacturer's specifications. Every boat owner must therefore weigh up the extent to which E10 makes sense for them. However, a fuel filter with water separator should always be installed - regardless of whether your boat runs on E10 or the more expensive alternative.
